The present disclosure relates to an image forming apparatus, and more particularly to a technology for estimating the amount of toner remaining in a toner container.
In an electrophotographic image forming apparatus, image development is achieved by feeding toner from a developing unit to an electrostatic latent image formed on the surface of a photosensitive drum or an intermediary transfer belt. The toner is contained in a toner container, and as the toner concentration in the developing unit lowers, the toner container is driven by a toner motor so that the toner inside the toner container is, while being stirred by a stirring paddle, supplied to the developing unit by a transport screw. Thus, the amount of drive of the toner container determines the amount of toner supplied to the developing unit.
In recognizing when to replace a toner container, it is essential to estimate the amount of toner remaining in the toner container. The amount of toner transported as a result of a transport screw being driven to rotate is constant. This makes it possible to estimate the amount of toner remaining in the toner container by estimating the amount of toner used based on the cumulative value of the number of revolutions of the transport screw. However, as the amount of toner in the toner container becomes small, the amount of toner transported with every single turn of the transport screw comes to vary. Thus, estimating the amount of toner used based on the cumulative value of the number of revolutions of the transport screw may lead to a large error. As a solution, for example, the amount of toner used is often calculated based on, for a period from the start of use of the toner container to a given time point, the length of time for which toner has been supplied and, thereafter, the number of pixels in toner images.